That's about the weakest PSU that I've ever seen..
I'm not sure that I want to take the chance with a 280W supply.
Plus, it seems like a higher rated PSU might run cooler that something
that's running at 92% of it's rating..?.
How about this one? It's extra green...
Newegg.com - Antec EarthWatts EA-500D Green 500W ATX12V v2.3 / EPS12V 80 PLUS BRONZE Certified Active PFC Power Supply